Question

Which determines the mode 1 in the Intel 8253?

(a) interrupt on terminal count

(b) programmable one-shot

(c) rate generator

(d) square wave rate generator

I got this question in class test.

I need to ask this question from Timer topic in division Basic Peripherals of Embedded Systems

Answer 1

Correct answer is (b) programmable one-shot

Explanation: Programmable one-shot is also known as mode 1 in the Intel 8253. In mode 1, a single pulse with a programmable duration is created first and then the pulse length is loaded into the counter and when the external gate signal is high, the rising edge starts the counter to count down to zero and the counter output signal goes high to start the external pulse. When the counter reaches to zero, the counter output goes low and thus the ending of the pulse.